Structural investigations of toluene diisocyanate (TDI) and trimethylolpropane (TMP)-based polyurethane prepolymer

Polyurethane prepolymer prepared from nonequivalent amounts of toluene diisocyanate (TDI) over trifunctional trimethylolpropane (TMP) was followed by gel permeation chromatography (GPC). Steric hindrance of TMP was considered as the main factor affecting the molar mass distribution, especially in the higher molecular weight region. An optimum reaction condition was the initial NCO/OH ratio of 3 and the reaction temperature of 50 °C. Then polyurethane prepolymer could be purified through the thin film evaporator with excellent properties. A combination of mass spectrometry (MS) and 1H nuclear magnetic resonance (NMR) spectroscopy was employed to identify and confirm the individual compounds presented from GPC analysis.